The LDR-HUB application Neurobiological Underpinnings of Math and Reading Comorbidity: A Twin Study proposes a framework to systematically integrate findings from the behavioral genetic, brain imaging, and reading/math disability literatures to examine some of the plausible mechanisms that affect variation and covariation in brain structure, brain function, math outcomes, and reading outcomes. The Research Project (Years 1 to 4) integrates structural and functional brain imaging within two ongoing longitudinal twin studies to address two Specifc Aims. For Specific Aim 1, we will select N = 300 pairs of 14 - 16 year old MZ and same-sex DZ twins from the Western Reserve Reading and Math Project (WRRMP: Based at Ohio State Univ. and Case Western Reserve Univ./Cleveland Clinic Foundation). For Specific Aim 2, we will select N = 100 pairs of 14 -16 year old same-sex DZ twins from the Colorado Learning Disabilities Research Center Twin Study (CLDRC: Based at the Univ. of Colorado), where one member of the CLDRC twin pair has been selected for Math Disability, Reading Disability, Math Disability + Reading Disability, or Neither Math nor Reading Disability. Across both aims, we will examine Domain-General and Domain-Specific relationships between brain structure, brain function, etiology, math outcomes, and reading outcomes with and without selection for disability. The Administrative Core (Years 1 to 4) will provide oversight of research activities, administer a mechanism for data sharing and dissemination, and supervise training and mentoring activities. The Developmental Core (Years 3 and 4) will solicit and administer seed grants extending the results of the Research Project, targeting both basic and applied research. In summary, the proposed work is a necessary starting point to address the larger questions of how math and reading disabilities develop and how they can be prevented and treated in light of substantial genetic, neurobiological, and environmental variation.